POS0790 18F-FLUORODEOXYGLUCOSE (FDG) PET-CT IMAGING OF SALIVARY GLANDS IN PRIMARY SJÖGREN’S SYNDROME AND ITS CORRELATION WITH ULTRASONOGRAPHIC SCORES AND SALIVARY FLOW RATE COMPARED TO HEALTHY CONTROLS
Authors: K. Abacar, T. N. Kissa, K. Oksuzoglu, T. Ones, G. Mumcu, G. Bruyn, N. Inanc
Journal: Annals of the Rheumatic Diseases (2022)

Background The use of salivary gland imaging modalities in patients with primary Sjögren’s syndrome (pSS) has been increasing recently. The contribution of each imaging method in terms of diagnosis or disease activity differs from each other. Although ultrasound and MRI are the most commonly used imaging modalities, the role of PET-CT for diagnosing pSS and determining glandular and extraglandular involvement has largely been neglected. Objectives This study aimed to compare the sizes and metabolic activities of the major salivary glands in patients with pSS and healthy controls (HC). Correlation of the 18 F-FDG PET-CT uptake characteristics with ultrasound scores and salivary flow rates of the patients and HC was also determined. Methods 22 patients with pSS and 10 age/sex-matched HC were included in the study. The sizes and FDG uptakes of the parotid and submandibular glands of pSS patients and HC were assessed by PET-CT. The maximum standardized uptake value (SUVmax) was evaluated for FDG uptakes, and each patient’s liver uptake and salivary gland uptake ratio were calculated. In addition, correlations of gland sizes and FDG uptakes in PET-CT with OMERACT and Hocevar ultrasound scores, stimulated and unstimulated SFR, ESSPRI dryness scores and disease durations of pSS patients were calculated by Spearman test. Results The mean age (SD) of the patients was 58.6 years (10.5) versus 58.6 years (19.1) of HC; the mean (SD) disease duration was 8.96 (8.77) years. ANA was positive in all patients, anti-SSA positivity was present in 82.6%, and 30.4% of patients experienced ≥1 parotid swelling episode. Compared to HCs, the mean size of both submandibular glands (p=0.006 for left and p=0.032 for right) and SUVmax of the left submandibular gland (p=0.044) were significantly smaller in patients with pSS. In pSS patients, both right and left parotid sizes were smaller and SUVmax uptake was greater than in HC; these differences however did not reach statistical significance. When the PET-CT involvement characteristics of the patients were compared with the salivary gland ultrasonography scores, there was a statistically significant negative correlation between the left parotid gland size in PET-CT and the ultrasonographic inhomogeneity of Hocevar score and OMERACT score. There was a statistically significant negative correlation between right parotid gland size measured on PET-CT with ultrasonographic inhomogeneity, hyperechoic foci, parenchymal echogenicity, Hocevar total score, and OMERACT score. No statistically significant correlation was found between SUVmax scores detected by PET-CT and ultrasound scores in both parotid glands and submandibular glands. A statistically significant positive correlation was found between the total gland size measured in PET-CT and the unstimulated salivary flow rate (p=0.038, r=0.604). There was a negative correlation between total gland size and ESSPRI dryness scores and symptom duration, which did not reach statistical significance. Conclusion PET-CT SUVmax measurements do not provide sufficient information for pSS-related involvement of the major salivary glands. Secondly, size measurement of the parotid glands by PET-CT is associated with OMERACT ultrasound scores, and also the sizes of both submandibular and parotid glands are smaller than HC. Table 1. Correlations of gland sizes and ultrasonographic scores Gland OMERACT Score Parenchymal Homogeneity Hypoechoic Areas Hiperechoic Visibility of Gland Border Parenchymal Inhomogenicity Total Size (PET/CT) Echogenity Foci R-Parotis r -.699* -.717* -.704* -0,598 -.656* -0,368 -.758** -.645* p 0,017 0,013 0,016 0,052 0,028 0,266 0,007 0,032 L-Parotis r -.699* -.717* -.704* -0,598 -.656* -0,368 -.758** -0,482 p 0,017 0,013 0,016 0,052 0,028 0,266 0,007 0,134 R-Subm r -0,011 0.118 -0,011 -0,270 0,203 -0,006 0,247 0.024 p 0,972 0.714 0,972 0,397 0,526 0,986 0,439 0.942 L-Subm r 0,245 0,306 0,245 0,071 0,327 0,118 0,306 0,435 p 0,443 0,333 0,443 0,826 0,300 0,714 0,333 0,158 Disclosure of Interests None declared